Conventional cars produce both gaseous pollutants and particulate matter such as PM2.5 and PM10.
Most of the particulate matter produced by cars is not produced by the engine or emitted through the exhaust. Only 10% of PM10 and 15% of PM2.5 emitted by cars is produced by the engine. The majority of the particulate pollution created is what’s termed “non-exhaust emissions” and is primarily produced by the interaction between the tyres on the road – road abrasion and tyre wear – and the break pads. The air wake of a car can also cause particles already on the ground to be blown up back into the air (resuspension). This can be seen when a large lorry passes by, and kicks up dust and dirty into the air.
Gaseous pollutants produced by cars are generally hydrocarbons (VOCs) as well as a few other gases such as nitrous oxides and sulphur oxides. They are emitted from the exhaust. These gases can often react with other chemicals in the air – such as ozone and other VOCs – to produce further gases and also particulate pollution.